Trouble Down Under: American Serena Williams is struggling with a left knee injury in the build-up to the defense of her Australian Open title as the world No.1 pulled out of the Hopman Cup. Williams is one of a host of leading players on the women's tour with injuries less than two weeks before the Melbourne major.
Last year Serena won three of the four grand slams in a stellar season for the American.
Maria Sharapova also joins Williams on the sidelines, after she was forced to withdraw from the Brisbane International draw with an inflamed left forearm. The Russian won the Brisbane title last year.
World No 2 Simona Halep has also pulled out of the Brisbane warm-up, citing a painful Achilles tendon which affected her in late 2015. "It's nothing dangerous, but it's still an inflammation", said the Romanian.
All eyes will now be on Roger Federer in Brisbane as he starts what he hopes will be another stellar season. The 34-year-old Swiss star said: "Every tournament I play is important to me. This is a tournament I want to win."